Performance Evaluation of the MOCO T In-Situ Combustion Project, Midway-Sunset Field

Abstract

Abstract This paper describes the analytical methodology applied to the MOCO T reservoir to match 27 years of dry in situ combustion project performance. It also serves to update previous technical papers on the project. project. A modification of the Nelson-McNiel Analytical model is introduced that provides excellent agreement with field performance. The correlating factor derived is found to be strongly dependent upon the product of the air requirements and volume burned. product of the air requirements and volume burned. Equations and graphical relationships are developed to show the recovery effects of various parameters such as air injected and volume burned. The calculated combustion front location also agrees well with produced fluid temperature maps. Close agreement between the calculated burned thicknesses and those obtained from recent seismic tomography efforts is also presented. The paper provides excess air, air-oil ratio, and oil-water ratio calculations as well as numerous graphical relationships that aided in an understanding of the reservoir, and may further improve process efficiency. process efficiency. These results demonstrate that analytical methods can be applied successfully to history match and predict future performance. It is believed that these results have direct applications to other reservoirs with similar parameters and characteristics. Introduction The MOCO T reservoir is located at the southern end of the Midway-Sunset Field. The project area originally contained 38 MMB (6.05 × 10(6) m3) of 14.5 API gravity (0.97 g/cm3) oil-in-place. The reservoir's moderate depth and net sand thickness as well as rock and fluid properties such as oil saturation, porosity, and viscosity lie well within the range of screening guides for thermally enhanced oil recovery processes. After consideration of the aforementioned characteristics, the in situ combustion process was determined to be the most technically and economically effective recovery mechanism for full field development. To date, the cumulative oil produced is 14 MMB (2.23 × 10(6) m3) and the cumulative produced is 14 MMB (2.23 × 10(6) m3) and the cumulative air injected is 59.5 BSCF (1.68 × 10(9) sm3). This paper provides a detailed discussion of the analytical methodology applied to obtain a 27-year history match of actual project performance. Also included is the subsequent analysis and interpretation of results observed and a forecast of future project performance. project performance. GENERAL RESERVOIR CHARACTERISTICS The 150 acre anticlinal reservoir is composed of six major sands separated by interbedded shales. Structural orientations varied from dips of 45 degrees in the north to 20 degrees in the south. The rock and fluid properties used in history match calculations are summarized in Table 1. PROJECT PERFORMANCE PROJECT PERFORMANCE The project's production and injection history is summarized in Figure 1. Air injection, into two wells, was initiated in January 1960 at a total rate of 2000 MSCF/D (56.6 × 10(3) sm3/d). Production was from the surrounding 26 wells. Spontaneous ignition occurred after 18 days of continuous injection. In early 1964, the air injection rate was increased to average 8000 MSCF/D (226.4 × 10(3) sm3/d). P. 623